1. Field of the Invention
The present invention relates to a DPCM (differential pulse code modulation) system adapted for compressing the quantity of information involved in the transmission of digital video signals.
2. Description of the Prior Art
In recording a digital color video signal on a magnetic tape, a great quantity of information has to be recorded. In an exemplary case of component color video data in the 4:2:2 mode, it becomes necessary to process data of about 216 megabits per second. When such huge quantity of information is to be recorded on a compact recording medium such as a cassette tape, the recording time is rendered extremely short owing to the fast tape speed that is required. In an attempt to solve this problem, resort has been had to the technique of band compression (also termed high efficiency encoding) to reduce the quantity of information to be recorded, thereby prolonging the recording time.
The DPCM (differential pulse code modulation) system, which compresses the difference between the anterior and posterior samples by non-linear quantization, is considered to be an effective band compression means for picture signals having mutual continuity and correlation.
In the DPCM system, a difference between the preceding decoded sample and an input sample is obtained and then is processed by non-linear quantization. Accordingly, in case any error exists in the decoded sample, a problem arises in that such error is propagated.